1. Technical Field
The present invention relates to a liquid charging apparatus and a liquid charging method for charging liquid such as ink into a liquid container such as an ink pack.
2. Related Art
An inkjet recording apparatus is known as a liquid ejection apparatus that ejects liquid such as ink onto a recording medium. Such an inkjet recording apparatus includes a recording head that ejects ink toward recording paper and an ink cartridge that stores ink to be supplied to the recording head.
To reduce the load applied to a carriage and reduce the size or the thickness of the inkjet recording apparatus, off-carriage type inkjet recording apparatuses have been introduced in which no ink cartridge is mounted on the carriage. Ink cartridges used in an off-carriage type inkjet recording apparatus have an ink pack storing ink, and the ink in the ink pack is supplied to a recording head through an ink supply tube.
Such an ink pack has a bag portion capable of storing ink and an outlet portion that, when the bag portion is pressurized with ink stored therein, discharges ink. The bag portion is formed of a film. Ink is charged into the bag portion by means of an ink charging apparatus. That is, the ink charging apparatus fills the bag with the ink stored in the ink tank, through the outlet portion. Thereafter, the outlet portion is sealed. At this time, it is preferable that the bag portion be filled with highly deaerated ink.
Japanese Laid-Open Patent Publication No. 2003-326730 discloses a liquid charging apparatus and a liquid charging method. In the technique disclosed in the publication, surplus ink is charged in a bag portion of an ink pack. Then, the bag portion is pressurized so that some of the ink, which is temporarily charged in the bag portion, is discharged through an outlet portion. Thereafter, a desired amount of ink is charged in the bag portion again, and the outlet portion is sealed. According to this technique, since some of the ink that has a high degree of dissolved air is discharged as surplus from the ink pack before the outlet portion is sealed to hermetically sealing the ink pack, the amount of air contained in the ink stored in the ink pack is reduced.
Japanese Laid-Open Patent Publication No. 2005-186343 discloses a configuration in which a deaeration unit is located in an ink pipe connecting an ink tank and an ink pack. The deaeration unit removes air dissolved in ink. Ink is supplied to the ink pack from the ink tank through the deaeration unit. Before the deaeration unit deaerates the ink supplied from the ink tank, the interior of the ink pipe is vacuumed to remove air from the ink pipe. Then, after removing the air from the ink pipe, ink is charged to the ink pack through the ink pipe.
According to the technique of Japanese Laid-Open Patent Publication No. 2003-326730, air can remain in the pipe connecting the ink tank to the ink pack. In such a case, when ink charging is performed using the same pipe after the pipe connects the ink tank and the ink pack, air in the pipe is mixed in the ink charged to the ink pack through the pipe, and the air is eventually dissolved in the ink. Thus, ink of a high degree of dissolved air is charged to the ink pack. After an excessive amount of such ink is charged, the charged ink needs to be discharged as waste ink. Accordingly, the efficiency of the liquid charging operation cannot be improved, and the apparatus construction is complicated.
According to the technique in Japanese Laid-Open Patent Publication No. 2005-186343, before charging ink from the ink tank to the ink pack while deaerating the ink, air is removed from the ink pipe. Thus, air in the ink pipe is not dissolved in the ink that is charged to the ink pack. However, other than the deaeration pump for removing air dissolved in ink, an air removing pump for removing air from the pipe needs to be provided in the pipe. This complicates the structure of the apparatus.